The radiation of Hymenoptera illuminated by Bayesian inferences from the fossil record

Determining when lineages originated provides fundamental insights into the timing and pace of their diversification, improving our understanding of transformative paleoevents such as the Angiosperm Terrestrial Revolution (ATR)¹ and Mid-Mesozoic Parasitoid Revolution (MMPR).² As the MMPR overlaps with the ATR, improved age estimates help to disentangle the dynamics and temporal succession of these events that shaped modern ecosystems. Hymenoptera (ants, bees, and wasps) played an important role in the MMPR and ATR through their parasitoid and pollinating lineages. Parasitoids impact trophic networks, whereas pollinators interact with flowering plants.³^,⁴ However, our understanding of Hymenoptera diversification remains limited by a lack of fossil-based studies and uncertainties in phylogenetic reconstructions. Combining fossil occurrences and macroevolutionary models, we estimated the origin and diversification of Hymenoptera lineages, considering changes in preservation over time and across taxa.⁵^,⁶^,⁷ Our results indicate that Hymenoptera diversification is multifaceted and lineage-specific. Sawflies diversified during the Paleozoic and Mesozoic in four episodes (middle Permian, Late Triassic to Middle Jurassic, Early Cretaceous, and the beginning of the Cenozoic) and experienced three extinction episodes (Middle Triassic, Late Jurassic, and mid-Cretaceous). The superfamily Xyeloidea originated during the middle Permian. Apocrita and parasitoid superfamilies emerged during the Early to Middle Triassic, diversified during the Late Jurassic and Early Cretaceous, and declined during the Late Cretaceous. We demonstrate that Hymenoptera experienced successive replacements during the MMPR-likely beginning in the Triassic-and synchronously with changes in floral assemblages of the ATR. We conclude with future directions to refine dating estimates from the fossil record.